Heart valve diseases are some of the most commonly diagnosed cardiac diseases in China, and are mostly found to be heart valve damage caused by rheumatic fever. In recent years, the continually aging population has driven an increasing incidence of valvular degeneration (including calcification, mucoid degeneration, etc.) and valvular damage caused by metabolic disorders in China.
Conventionally, heart valve replacement surgery is an open-heart procedure conducted under general anesthesia, during which, following an incision made along the patient's sternum (sternotomy), the heart is stopped and blood flow is guided through a “heart-lung” bypass machine (extracorporeal circulation machine). Therefore, traditional open surgery brings to the patient significant trauma as well as possible transient disturbances caused by emboli and other issues associated with the use of the heart-lung machine Complete recovery from the trauma typically costs a couple of months. For some special population groups such as elders, the trauma is particularly unendurable and the recovery needs more time and is sometime even impossible.
Minimally invasive interventional surgery offers a variety of advantages, including needlessness of sternotomy, minimal patient trauma and quick recovery. In the recent ten years, the development shows that not only the diseases curable by traditional medical and surgical treatments but also some diseases that the traditional approaches could not handle can be treated by the interventional therapies. After entering the twenty-first century, researches on interventional therapies for valvular heart diseases have been experiencing a notable acceleration. Percutaneous valve implant techniques have evolved from experimental researches to small-scale clinical trials and are likely to have breakthroughs in technical “bottlenecks” to achieve extensive clinical applications. This makes the techniques again a focus of research efforts in the field of interventional cardiology.
The success of a minimally invasive procedure for implanting a prosthetic valve is critically dependent on how to deliver the prosthetic valve with a delivery system to a target site with ensured coaxial alignment between a sheath carrying the prosthesis and the original valvular lumen (annulus) until accurate positioning and deployment have been achieved.
U.S. patent Pub. No. US2011/0251683A1 describes a delivery system capable of loading or deploying a prosthetic heart valve by rotating or pushing/pulling operations. In addition, the system provides positioning and deployment functions, as well as a recapturing function when needed, by virtue of a design composed of an inner tube, a sheath and a stability tube. The sheath of the delivery system is homogenously a formed polymer tube, a braided polymer tube or a cut metal tube. During the recapturing process, the stability tube is advanced, increasing circumferential support of a prosthesis-retaining section of the sheath to the prosthesis and thereby effectuating the recapturing. The stability tube of the delivery system is a braided polymer tube. In addition, the Chinese patent document CN101961269A discloses a prosthetic valve delivery system including a sheath which is a polymer tube embedded with a metal braiding.
In the conventional delivery systems for use in interventional procedures, positioning accuracy is, however, not taken into account in the design of such sheaths homogenously as a formed polymer tube, a braided polymer tube or a metal tube for loading and retaining the prosthetic heart valve. Conventionally, in order to achieve the coaxial positioning, additional operating means for the delivery systems are sometimes utilized, as well as catheter steering mechanisms. However, additional difficulties in surgical operations are resulted from the directional requirements for advancement of the catheter of the delivery system in a vascular lumen, i.e., the catheter being required to so bend as to be adapted to the geometric profile of the vascular lumen.
Therefore, in the prior art, there are the following technical problems: 1) the design of the delivery systems does not take into account both the improving of positioning accuracy and prevention of the over-expansion of the sheath; and 2) positioning achieved by an additional steering function of the handle leads to increased difficulties in surgical operations.